The present invention relates generally to a solvent composition for cleaning organics as well as water or water residue from metallic surfaces, and more particularly to such a solvent composition that is relatively nonhazardous, of low toxicity, and suitable for cleaning surfaces of radioactive materials.
The removal of organic contaminates, usually in the form of oily or greasy films, from surfaces of metallic materials has been previously achieved by using solvents that are now considered to be hazardous. For example, a halogenated hydrocarbon such as trichloroethylene, 1,1,1-trichloroethane, tetrachloroethylene, or 1,1,2-trichloro-1,2,2-trifluoroethane was frequently used as a fire suppressor in combination with a relatively volatile aliphatic hydrocarbon solvent such as nonane for forming a degreasing solvent. Such chlorinated or chlorofluorocarbon solvents have been satisfactorily utilized for some time in both vapor and hand degreasing modes for cleaning surfaces of metallic materials, including radioactive materials. However, relatively recent investigations into the use of these chlorinated or chlorofluorocarbon solvents have shown that they are hazardous and toxic to the health of humans as well as hazardous to the environment such as by causing the unfavorable depletion of the ozone layer about the earth. As a result of such investigations, legislation, notably the Resource Conservation and Recovery Act (RCRA), has resulted in regulations which list such chlorinated and chlorofluorocarbon solvents as being hazardous so as to require the use of special handling, storage, and processing procedures for these solvents and solvent-contaminated waste from cleaning operations.
This invention was made with the support of the U.S. Government under contract No. DE-AC05-84-OR21400 awarded by the U.S. Department of Energy. The U.S. Government has certain rights in this invention.
These regulations have had a significant impact on the use of such metal degreasing solvents especially when they are used to degrease surfaces of radioactive materials in that any waste or residue resulting from the cleaning operation is classified as "mixed" waste since the waste contains both a solvent considered to be hazardous by RCRA regulations and a radioactive material. Under existing conditions, the presence of such mixed waste creates significant handling and storage problems since no facilities have been permitted to process mixed waste. The only presently acceptable procedure for handling mixed waste is to store the waste in limited quantities and space under conditions subject to strict control for possible future processing. Thus, waste in the form of various paper and cloth wipes, coveralls, lab coats, gloves, mop heads and the like used for degreasing surfaces of radioactive materials with a solvent designated as hazardous under RCRA must be handled as mixed waste. Accordingly, due to this mixed waste classification, the use of solvents such as chlorinated and chlorofluorocarbon solvents that are listed as being hazardous under RCRA regulations is no longer considered to be a viable option for cleaning the surfaces of radioactive materials. In fact, the use of such listed solvents for cleaning nonradioactive hard metal surfaces is of questionable value since the residue from such cleaning operations must be treated as hazardous waste and, as such, requires specific handling and processing steps for the storage or disposal of the waste.
Extensive efforts have been conducted in an effort to provide a solvent that is not considered to be hazardous by RCRA regulations for effectively degreasing surfaces of radioactive materials. However, in addition to finding a desirable degreasing solvent which satisfies RCRA regulations there are numerous other requirements that the solvent should possess for acceptance in the work place. Such other requirements dictate that the solvent be characterized by acceptable exposure levels by industrial hygiene standards, relatively low flammability properties, environmental emissions control, acceptable nuclear criticality factor, and high levels of quality control. Also, when attempting to replace chlorinated and chlorofluorocarbon type solvents with nonhazardous solvents which satisfy metal-surface degreasing requirements as provided by the use of highly satisfactory but hazardous, degreasing solvents such as 1,1,1-trichloroethane or 1,1,2-trichloro-1,2,2-trifluoroethane, as well as satisfactorily fulfilling the other solvent requirements noted above, it was found that one additional problem needed to be addressed. For example, the machining of radioactive materials such as uranium and uranium alloys is usually achieved with aqueous-based machining coolants and lubricants. Also, the surfaces of such materials are frequently rinsed with water or aqueous solutions after the machining operation. The presence of residual quantities of such aqueous solutions and/or water on the surfaces of uranium and uranium alloys following machining are undesirable since such residual aqueous solutions or water will promote uneven corrosion and staining of the machined surfaces. Corresponding corrosion and staining problems will also be present on the surface of other hard metals which utilize aqueous machining lubricants and coolants and/or the rinsing of machined surfaces with water or aqueous solutions. Thus, an acceptable relatively nonhazardous solvent should provide desirable degreasing properties as well as the capability of undercutting and displacing water from the metal surfaces.